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residential chilled water systems

Just a side note, take a close look at the Mitsubishi City Multi web site. This is a single outdoor unit (heat pump) with a central distribution box inside and then you can pipe I think up to 16 air handlers off that. Outdoor units start at 4 ton I think and now go up to 20. You can run heating & cooling at the same time. and when both are running thats when you get the highest efficiency. Great for multi air handler jobs, very quiet with a turn down to 15% of full capacity. Uses a inverter compressor with bypass + variable speed indoor units, ducted or non ducted.

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Comments

who out there is doing residential chilled water systems? What are the pros and cons to these installs? I am bidding a job rite now and the home owner wants a quote on both chilled water and condensor style for his cooling. Thanks

Probably the biggest advantage of installing a chilled water system is that you do not have to run refrigerant lines between the indoor and outdoor units.

Since the chiiler will likely be a packaged system, the refrigerant charge is determined and introduced to the system at the factory. You only need to run the water lines to and from the water coils in the duct system.

Another big advantage to the chilled water system is that the air handler will not reuired nearly as much service, as you have little more than a fan-coil unit. This makes troubleshooting a breeze.

Good luck with the system.

The Professor

P.S. Please post future cooling questions in the "Ask Professor Silberstein" area so we can keep the threads/topics organized!

when over say 7.5 to 10 tons. The biggest house I designed had a 90 ton air-cooled chiller and another had a 46 ton chiller, split system air cooled, just to illustrate the possibilities. Professor Silberstein is absolutely right about the benefits, especially distance. Noise can be isolated by being more remote.

Cautionary note: If you do not have 3-phase power available you may have to split up the compressors into roughly 1.5 to 2 HP chunks, the largest you can usually get on single-phase power. Thus a 12-ton chiller might have 5 or 6 compressors and more expensive wiring. First cost generally is higher; part of that is distance-related and the associated insulation of both supply and return lines. Glycol is another; you may consider that factor or seasonal lay-up.

With some systems (I specify TSI/Rae Corp. chillers out of Pryor, Oklahoma) you can use the hot gas to pre-heat domestic water or use pool water as a heat sink/condensing medium.

How about integration with Radiant Floor heat? We have been doing this for a while. We have a 50 gallon buffer tank that the chiller/reverse chiller feeds into. You can use air handlers for cooling or even a second stage of heat, and design your radiant floor heat for 90 degree supply temps. One of my customers claims that he has $50/month heating bills for his 6,000 square foot home.

Chilled water systems with chilled water storage (whether phase change or not) are used in big applications, airports, museums and such. The advantages are mainly peak demand shaving (for commercial rates) and better performance since the system does not have to work the hardest when the outdoor conditions are the worse.

How small can you go and still have a chilled water storage system that makes sense? I would like to make ice water at night only and melt it the next day or so.

It seems to me, the advantage of a storage tank (if there is any for residential applications) would help justify the extra chilled loop install.

Today, I ate my first ice cream for the season, and it froze my brain.

Another advantage of chilled water systems is that you can adapt them to whatever cooling machine is most cost effective for the market conditions. When natural gas was so cheap a few years back I was really turned on by absorption systems, if such conditions were to come back, only a simple plug in would be needed.

As far as chillers are concerned, I have applied them as small as a few tons, mostly for process work but for the occasional house. I applied an 8-ton chiller for the Boston University Boathouse; it worked out better than a few split systems would have, glycol application included.

Now the storage part: I do not know where the economic break-even point might be and at what scale... The average ice storage systems I have been involved with were over 1,000 tons. Naturally your night-time electric rates and daytime demand rates make it all happen or not.

York had or has a storage system consisting of HDPE "balls" filled with brine of some sort. I am not sure how they were chilled but it seems a scalable technology. The Trane-marketed Calmac systems used thin sheets of ice between plates or scrolls, which escapes me at the moment. I do not see that is usable for small systems. Interesting to explore...

A company called Servel had an open system gas-fired absorber, not sure if it is still available and under what name. It came in 5-ton increments. As you know with absorbers, getting water much lower than 43 degrees takes some effort; making ice would not be an option. Not that you were suggesting that, just to lay it out though.

There you go, install a 1000 ton storage system, turn it on for a fraction of a second on, say June 1, and be done with the cooling needs of your home for the rest of the summer... That'll defrost our public power utilities.

Thanks for the reply.

I did look into the ping pong balls storage. The info I had was from a French company (I can't remember the name right now) that had done several big projects in the US, I want to say, the Atlanta airport, and a museum in Chicago, and something with the chilled district system in Orlando and a bank tower in Cincinnati, or at least maybe just one of them.

Their big claim for justifying the ping pong ball system which is much more expensive than just plain water is that the balls are filled with a custom tailored juice that changes phase at the (higher/lower than 32F) temperature you want your system at. The chilled water flows around them.

The only way to pack a significant load of BTU is to rely on a phase change. And if I remember right again, they where suggesting their storage as ideal for those systems not running at freezing temperature. Plus, the individual balls don't form one giant ice cube that doesn't melt fast enough, it's like a snow cone melting down your sleeve.

There were a bunch of these (the Arkla-Servel units) in my area, but only saw one that was working correctly. At one time, they were known as break down units. Some people said they may run about a month without a break down.

I've designed a bunch of reversible heat pump hydronic systems (4-pipe and one 2 pipe). They are very efficient, quiet and easy to stage. I typically use an 80 thermal tank and am very please with the ability of these systems to reduce humidity and not over cool the space.

arkla servel used to make a furnace with an absorber built into it. We got a lot of complaints about noise. They sounded like someone pouring bb's down a sheetmetal chute. Bryant made absorbers in 3,5 and 7 ton sizes. Amonia was the refrigerant and water was the absorbent. Back in the sixtys the gas co around the Chi. area had a promotion. They would finance them and gave 5 yrs free service. We installed them and never saw them again. I heard they had lots of problems.

Near the Albany, NY area we are selling a lot of 3 and 5 ton reverse cycle chillers for the high end residential market. It started when a homeowner didn't want to see the condensers next to the home. We asked where would you like them and they said out of sight over a bank. We ended up selling 2-5 ton Spacepak Chillers and put them 90 feet from the house. Since then, we've sold 14 more and up to 200' away from the home. Very effecient, quiet, green, and excellent factory support by the reps and manufacturer personell. We're working out a few small bugs like the condensation around the pumps ect; in the mechanical room, but for the most part it is a great system.

Was approved by PUC & electric utilities in Florida in the seventies. Ice maker rejected heat to hot water storage. Machine ran at night to store domestic hot water and ice for air conditioning. One issue was how much less is electric demand at night in Florida.